Rokubungi is the Japanese word for sextant. The Kanji for it is as follows, ( Ï»Éå±· ) (EUC Encoded).

In the anime Neon Genesis Evangelion, numerous nautical references are used by the creator, Anno Hideaki, when it comes to naming characters. Most are named after former Imperial Japanese Warships (for example Akagi), however some are simply named after nautical terms. Gendou Rokubungi is the original name of the character more commonly known as Gendou Ikari in the series. Gendou replaced Rokubungi as his last name when he married Yui Ikari. Incidentally the Japanese word Ikari means 'anchor'.

Kanji source: Japanese-English Ocean Dictionary - http://www.sainet.or.jp/~k-naka/